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    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var result = parseInt(prompt("请输入一个年份"));
        if ((result % 4 == 0 && result % 100 !=0) || result % 400 == 0) {
            alert("闰年")
        }else{
            alert("不是闰年")
        }
    </script>
</body>
</html>